A variable draft vessel and a method and system of deballasting a vessel

A method of deballasting a vessel having at least one ballasting tank and at least one port in fluid communication with the at least one ballasting tank arranged to selectively adjust the flow of ballast water in and out of the at least one ballasting tank. The method comprises removing a downward force on the vessel (102) exerted by an offshore installation (100) positioned above or near the vessel (102). The method further comprises raising the vessel (102) from a second draft (d2) to a first draft (d1) due to a buoyancy force on the vessel (102). The method also comprises opening the at least one port (222) when the vessel (102) is at the first draft (d1). The method also comprises emptying at least some of the at least one ballasting tank (200).